<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Button</title>
</head>
<body>
    <button class="btn">Yes!</button>
    <br><br>
    <button class="btn ok"> OK </button>
</body>
<style>
html{
    font-size: 16px;
}
button{
    padding: .3rem .8rem;
    border: 1px solid rgba(0,0,0, .1);
    background: #58a linear-gradient(hsla(0, 0%, 100%, .2), transparent);
    border-radius: .2em;
    box-shadow: 0 .05em .25em rgba(0,0,0,.5);
    color: white;
    text-shadow: 0 -.05em .25em rgba(0,0,0,.5);
    font-size: 1.25rem;
    line-height: 1.5;
    outline: none;
    cursor: pointer;
}
button.ok{
    background-color: #6b0;
}
    </style>
</html>